Oil strainers are one example of a product form of a hollow body, in which two half parts are coupled to each other with an internal member fitted with the half part so that the internal member is provided inside the hollow body. The oil strainer is a component for filtering the engine oil used for the lubrication of automobile engines. The oil strainer includes an oil filter, which is the internal member fitted into the half parts.
Techniques for coupling two half parts in an oil strainer are disclosed in Japanese Publication for Unexamined Publication Nos. 42709/1999 (Tokukaihei 11-42709, published on Feb. 16, 1999) (Prior art 1), and 2001-280207 (published on Oct. 10, 2001) (Prior art 2).
Prior art 1 describes roughly three different structures for two half parts. In one structure, as shown in FIG. 9(a), an upper half part 100 has raised portions 300 and 400 that extend from the sides of the upper half part 100 on the surface facing a lower half part 200. The lower half part 200 has a raised portion 500 that extends from a central portion of the surface facing the upper half part 100. The upper half part 100 and the lower half part 200 having the foregoing constructions are welded to each other by vibration welding to incorporate an oil filter 600, as shown in FIG. 9(b).
In the second structure, as shown in FIG. 10(a), an upper half part 110 has a raised portion 310 that extends from a central portion of the surface facing a lower half part 210. The lower half part 210 has a raised portion 510 that extends from a central portion of the surface facing the upper half part 110. The upper half part 110 and the lower half part 210 having the foregoing constructions are welded to each other by heat-plate welding to incorporate the oil filter 600, as shown in FIG. 10(b).
In the third structure, as shown in FIG. 11(a), an upper half part 120 has two raised portions 320 and 420 that extend from the sides of the upper half part 120 and from the surface facing a lower half part 220. The lower half part 220 has a raised portion 520 that extend from a central portion of the surface facing the upper half part 120. The upper half part 120 also has a recessed portion 700, corresponding in shape to the raised portion 520, on the surface facing the lower half part 220. The upper half part 210 and the lower half part 220 having the foregoing constructions are welded to each other by spin welding to incorporate the oil filter 600, as shown in FIG. 11(b).
In the technique disclosed in Prior art 2, as shown in FIG. 12(a), an upper half part 800 is moved toward a lower half part 900 (in the direction of arrow A in FIG. 12(a)), so as to weld an oil filter 1000 by vibration welding between the upper half part 800 and the lower half part 900. The upper half part 800 has a raised portion 810 that extends from a central portion of the surface facing the lower half part 900. The lower half part 900 has a raised portion 910 that extends from one side of the lower half part 900 on the surface facing the upper half part 800. The lower half part 900, together with the oil filter 1000, forms a raised portion 1100 on a position facing the raised portion 810 of the upper half part 800.
One problem of the foregoing prior art techniques, however, is that they are not suitable for coupling two half parts by heat welding. The following discusses the reasons why such a problem is caused.
In the technique disclosed in Prior art 1, when the upper and lower half parts are to be coupled to each other using a flat heat plate, the heat plate needs to be placed between the upper half part 100 and the lower half part 200, as shown in FIG. 9(a). Consequently, the heat plate is in contact with the raised portions 300, 400, and 500.
The problem of this is that the heat plate in contact with the raised portions 300 and 400 melts the raised portions, and, in the state shown in FIG. 9(b), exposes the coupled site of the upper half part 100 and the lower half part 200, with the result that the final product is cosmetically unappealing. The heat plate may be modified to have a recessed portion that corresponds in shape to the raised portion 500, so as to prevent the raised portions 300 and 400 from being melted. However, this is not advantageous because the complex structure of the heat plate raises the manufacturing cost.
This problem also resides in the structure described with reference to FIG. 11(a) in connection with Prior art 1. Namely, the flat heat plate used to weld the half parts melts the raised portions 320 and 420 of the upper half part 120 when the half parts are welded. As a result, the coupled site of the upper half part 120 and the lower half part 220 is exposed.
The same problem is also caused in the structure described with reference to FIG. 12(a) in connection with Prior art 2. Namely, the flat heat plate used to weld the half parts melts the raised portion 910 of the lower half part 900, exposing the coupled site of the upper half part 800 and the lower half part 900. This problem occurs because the raised portion 910 is closer to the upper half part 800 than the raised portion 1100.
Meanwhile, the structure described with reference to FIG. 10(a) in connection with Prior art 1 is associated with the following problem. Namely, owning to the fact that the surface of the upper half part 110 facing the lower half part 210 does not have a raised portion that extends from a side portion of the surface, the coupled site of the raised portion 310 and the raised portion 510 is exposed when the half parts are coupled together. As a result, the appearance of the final product may be impaired as in the foregoing prior art techniques.